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DS1857

Dual Temperature-Controlled Resistors with

External Temperature Input and Monitors

______________________________________________ Maxim Integrated Products 1

For pricing delivery, and ordering information please contact Maxim/Dallas Direct! at

1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.

General Description

The DS1857 dual temperature-controlled nonvolatile

(NV) variable resistors with external temperature input

and monitors consists of two 50kΩ 256-position linear

variable resistors, two analog monitor inputs (MON1,

MON2), and an external temperature sensor input. The

device provides an ideal method for setting and tem-

perature-compensating bias voltages and currents in

control applications using minimal circuitry. The vari-

able resistor settings are stored in EEPROM memory

and can be accessed over the 2-wire serial bus.

Applications

Optical Transceivers

Optical Transponders

Instrumentation and Industrial Controls

RF Power Amps

Diagnostic Monitoring

Features

♦ Four Total Monitored Channels (Temperature,

, MON1, MON2)

♦ Two External Analog Inputs (MON1, MON2)

♦ Interface to External Temperature Sensor (LM50)

♦ Two 50kΩ, Linear, 256-Position, Nonvolatile

Temperature-Controlled Variable Resistors

♦ Resistor Settings Changeable Every 2°C

♦ Access to Monitoring and ID Information

Configurable with Separate Device Addresses

♦ Resistor Disable (Open-Circuit) Function

♦ 2-Wire Serial Interface

♦ Three Address Lines for Multiple Devices

♦ Operates from a 3.3V or 5V Supply

♦ SFF-8472 Compatible

Ordering Information

Rev 0; 1/03

PART

TEMP RANGE

PIN-PACKAGE

DS1857E-050

-40°C to +95°C

16 TSSOP

DS1857E-050/T&R

-40°C to +95°C

16 TSSOP

(Tape-and-Reel)

DS1857B-050

-40°C to +95°C

16 Ball CSBGA

TOP VIEW

16-BALL CSBGA (4mm x 4mm)

1.0mm PITCH

16 TSSOP

324

EXTTMP

A0WPENRHIZ

MON2MON1L0GND

H1V

SCLA1

L1H0SDAA2

DS1857

SDA

SCL

WPEN

RHIZ

GND

EXTTMP

MON2

MON1

Pin Configurations

DS1857

SDA

0.1µF

SCL

A0**

A1**

A2**

WPEN

RHIZ

GND

EXTTMP

MON2

MON1

Tx DISABLE

TO EXTERNAL TEMPERATURE

SENSOR, SUCH AS LM50

DIAGNOSTIC

INPUTS

0 TO 2.5V FS

TO LASER BIAS

CONTROL

TO LASER MODULATION

CONTROL

DECOUPLING

CAP

Rx POWER*

Tx BIAS*

*Rx POWER AND Tx BIAS CAN BE ARBITRARILY

ASSIGNED TO THE MON INPUTS.

**ADDRESS INPUTS DETERMINE THE MAIN DEVICE 2-WIRE

SLAVE ADDRESS WHEN ADFIX = 0. THIS ADDRESS MUST BE

DIFFERENT THAN THE AUX DEVICE ADDRESS WHEN ADEN = 0.

= 3.3V

4.7kΩ4.7kΩ

2-WIRE

INTERFACE

GROUND TO

DISABLE WRITE

PROTECT

Typical Operating Circuit

Summary of content (22 pages)

PAGE 1
Rev 0; 1/03 Dual Temperature-Controlled Resistors with External Temperature Input and Monitors The DS1857 dual temperature-controlled nonvolatile (NV) variable resistors with external temperature input and monitors consists of two 50kΩ 256-position linear variable resistors, two analog monitor inputs (MON1, MON2), and an external temperature sensor input. The device provides an ideal method for setting and temperature-compensating bias voltages and currents in control applications using minimal circuitry.
PAGE 2
DS1857 Dual Temperature-Controlled Resistors with External Temperature Input and Monitors ABSOLUTE MAXIMUM RATINGS Voltage on VCC Relative to Ground.......................-0.5V to +6.0V Voltage on Inputs Relative to Ground* ................................................-0.5V to VCC + 0.5V Voltage on Resistor Inputs Relative to Ground* ................................................-0.5V to VCC + 0.5V Current into Resistors............................................................
PAGE 3
Dual Temperature-Controlled Resistors with External Temperature Input and Monitors (VCC = 3.0V to 5.5V, TA = -40°C to +95°C, unless otherwise noted.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Position 00h Resistance TA = +25°C 0.70 1.0 1.25 kΩ Position FFh Resistance TA = +25°C 40 50 60 kΩ Absolute Linearity (Note 6) -2 +2 LSB Relative Linearity (Note 7) -1 +1 LSB Temperature Coefficient (Note 8) High-Z Resistor Current IRHIZ 50 RHIZ = VCC ppm/°C 0.
PAGE 4
DS1857 Dual Temperature-Controlled Resistors with External Temperature Input and Monitors AC ELECTRICAL CHARACTERISTICS (VCC = 3.0V to 5.5V, TA = -40°C to +95°C, unless otherwise noted.
PAGE 5
Dual Temperature-Controlled Resistors with External Temperature Input and Monitors (VCC = 3.0V to 5.5V, TA = -40°C to +95°C, unless otherwise noted.) Note 11: After this period, the first clock pulse is generated. Note 12: The maximum tHD:DAT only to has be met if the device does not stretch the LOW period (tLOW) of the SCL signal.
PAGE 6
Typical Operating Characteristics (continued) (VCC = 5.0V, TA = +25°C, unless otherwise noted.) RESISTOR 0 INL (LSB) RESISTOR 0 DNL (LSB) 0.2 0.1 0 -0.1 -0.2 -0.3 0.4 0.3 RESISTOR 1 INL (LSB) RESISTOR 0 DNL (LSB) 0.15 DS1857 toc07 0.3 0.5 DS1857 toc06 0.4 RESISTOR 1 INL (LSB) 0.25 DS1857 toc05 0.5 RESISTOR 0 INL (LSB) 0.05 -0.05 -0.15 0.2 0.1 0 -0.1 -0.2 -0.3 -0.4 -0.4 -0.5 -0.25 0 25 50 75 100 125 150 175 200 225 250 -0.
PAGE 7
Dual Temperature-Controlled Resistors with External Temperature Input and Monitors PIN BALL NAME FUNCTION 1 B2 SDA 2-Wire Serial Data Interface. This pin is for serial data transfer to and from the device. 2 A2 SCL 2-Wire Serial Clock Interface. The serial clock input is used to clock data into and out of the device. 3 C3 A0 Address Input. The address input pins specify the 2-wire address of the device (when ADFIX = 0). 4 A1 A1 Address Input.
PAGE 8
DS1857 Dual Temperature-Controlled Resistors with External Temperature Input and Monitors PROT AUX PROT MAIN AD PROT MAIN MD MD AD (AUXILIARY DEVICE ENABLE A0h) A0 TABLE SELECT DEVICE ADDRESS A1 A2 MD (MAIN DEVICE ENABLE) DEVICE ADDRESS EEPROM 128 x 8 BIT 00h-7Fh ADDRESS R/W ADDRESS ADEN ADFIX SDA EEPROM 72 x 8 BIT 80h-C7h ADDRESS TABLE 02 RESISTOR 0 LOOK-UP TABLE R/W STANDARDS TABLE SELECT EEPROM 72 x 8 BIT 80h-C7h TABLE 03 RESISTOR 1 LOOK-UP TABLE R/W ADDRESS 2-WIRE INTERFACE TE
PAGE 9
Dual Temperature-Controlled Resistors with External Temperature Input and Monitors SIGNAL +FS SIGNAL +FS (hex) -FS SIGNAL -FS (hex) Temperature 127.996°C 7FFF -128°C 8000 VCC 6.55V FFFF 0V 0000 MON1 2.5V FFFF 0V 0000 MON2 2.5V FFFF 0V 0000 Table 3. Look-up Table Address for Corresponding Temperature Values TEMPERATURE CORRESPONDING LOOK-UP TABLE ADDRESS <-40°C 80h -40°C 80h -38°C 81h -36°C 82h -34°C 83h Table 2.
PAGE 10
DS1857 Dual Temperature-Controlled Resistors with External Temperature Input and Monitors Table 5. ADEN and ADFIX Bits Table 4. ADEN Address Configuration ADEN (ADDRESS ENABLE) NO.
PAGE 11
Dual Temperature-Controlled Resistors with External Temperature Input and Monitors Memory Description Main and auxiliary memories can be accessed by two separate device addresses. The Main Device address is determined by address pins or value in Table 01 byte 8Ch, when ADFIX = 1 (see Table 5). The Auxiliary Device address is A0h. A user option is provided to respond to one or two device addresses.
PAGE 12
DS1857 Dual Temperature-Controlled Resistors with External Temperature Input and Monitors Register Map A description of the registers is below. The registers are read only (R) or read/write (R/W). The R/W registers are writable only if write protect has not been asserted (see the Memory Description section).
PAGE 13
Dual Temperature-Controlled Resistors with External Temperature Input and Monitors DS1857 Main Device (continued) MEMORY LOCATION (hex) EEPROM/ SRAM R/W DEFAULT SETTING (hex) 1C to 5F EEPROM — 00 Reserved Digitized measured value for temperature. See Table 1. Digitized measured value for VCC. See Table 1.
PAGE 14
DS1857 Dual Temperature-Controlled Resistors with External Temperature Input and Monitors Main Device (continued) MEMORY LOCATION (hex) 6 5 14 EEPROM/ SRAM — — R/W R/W R/W DEFAULT SETTING (hex) 0 0 NAME OF LOCATION FUNCTION VCCU This bit goes high after a VCC update has occurred for the corresponding measurement in bytes 62h to 63h. This bit can be written to a 0 by the user and monitored to verify that a conversion has occurred.
PAGE 15
Dual Temperature-Controlled Resistors with External Temperature Input and Monitors MEMORY LOCATION (hex) EEPROM/ SRAM R/W DEFAULT SETTING (hex) NAME OF LOCATION FUNCTION 4 — — — VCClo This alarm flag goes high when the lower limit of the VCC setting is violated. 3 — — — MON1hi This alarm flag goes high when the upper limit of the MON1 setting is violated. 2 — — — MON1lo This alarm flag goes high when the lower limit of the MON1 setting is violated.
PAGE 16
DS1857 Dual Temperature-Controlled Resistors with External Temperature Input and Monitors Table 01h MEMORY EEPROM/ LOCATION SRAM (hex) 16 R/W DEFAULT SETTING (hex) NAME OF LOCATION FUNCTION Mode — 80 SRAM R/W Bit 7 — — 0 X — 6 — — 0 X — 5 — — 0 X — 4 — — 0 X — 3 — — 0 X — 2 — — 0 X — 1 — — 1 TEN If TEN = 0, the temperature conversions update and the resistors can be controlled manually.
PAGE 17
Dual Temperature-Controlled Resistors with External Temperature Input and Monitors MEMORY EEPROM/ LOCATION SRAM (hex) R/W DEFAULT SETTING (hex) NAME OF LOCATION FUNCTION 5 — — 0 ADEN Controls if the device responds to one or two device addresses (see the Memory Description section and Table 5). 4 — — 0 ADFIX Controls the means by which Main and Auxiliary Device addresses are set (see the Memory Description section and Table 5). 3 — — 0 APEN Controls auxiliary write protect.
PAGE 18
Temperature Conversion Temperature is sensed from an external sensor. The sensor’s scale is +10mV/°C for gain and +500mV for offset at 0°C. The DS1857 accommodates a temperature range of -40°C to 102°C for its look-up tables. The resistor look-up tables are stepped through according to this temperature every 2°C. The relationship between the voltage and temperature is shown in Equation 2. T= V − 0.
PAGE 19
Dual Temperature-Controlled Resistors with External Temperature Input and Monitors Write Operations After receiving a matching address byte with the R/W bit set low, provided there is no write protect, the device goes into the write mode of operation (see the Memory Organization section). The master must transmit an 8-bit EEPROM memory address to the device to define the address where the data is to be written.
PAGE 20
DS1857 Dual Temperature-Controlled Resistors with External Temperature Input and Monitors 2-Wire Serial Port Operation The 2-wire serial port interface supports a bidirectional data transmission protocol with device addressing. A device that sends data on the bus is defined as a transmitter, and a device receiving data as a receiver. The device that controls the message is called a master. The devices that are controlled by the master are slaves.
PAGE 21
Dual Temperature-Controlled Resistors with External Temperature Input and Monitors appropriate device address bits, and the read/write bit, the slave device outputs an acknowledge signal on the SDA line. Chip Topology TRANSISTOR COUNT: 44149 SUBSTRATE CONNECTED TO GROUND.
PAGE 22
DS1857 Dual Temperature-Controlled Resistors with External Temperature Input and Monitors SDA tBUF tHD:STA tLOW tR tSP tF SCL tHD:STA STOP tSU:STA tHIGH tSU:DAT START REPEATED START tSU:STO tHD:DAT Figure 6. 2-Wire AC Characteristics Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.